Code block as template argument

[Steven Schveighoffer]

On 2/11/20 10:30 AM, Виталий Фадеев wrote:
> On Tuesday, 11 February 2020 at 14:58:58 UTC, Andrea Fontana wrote:
>> On Tuesday, 11 February 2020 at 11:34:49 UTC, Ali Çehreli wrote:
>>> On 2/11/20 3:14 AM, Виталий Фадеев wrote:> On Tuesday, 11 February 
>>> 2020 at 11:10:44 UTC, Виталий Фадеев wrote:
>>>
>>> > Analog C-code with macros:
>>> >      #define TPL(M,D,CODE) if ( state & M && diraction = D )
>>>
>>>                                                ^^^^^^^^^^^^^
>>> [...]
>>>
>>> // Option 1: Equivalent of a C macro
>>> void executeMaybe(Func)(uint M, Direction D, Func func) {
>>>   if ((state & M) && (direction == D)) {
>>>     func();
>>>   }
>>> }
>>>
>>> [...]
>>>
>>> Ali
>>
>> The C code apparently does an assignment inside the macro.
> 
> Wow! Thank! I mass.
> I was mean comparation:
> Analog C-code with macros:
>      #define TPL(M,D,CODE) if ( state & M && diraction == D ) CODE;
> example code
>      TPL( OPEN, OUT,
>        {
>          delete AppsWindow
>          state &= !OPEN
>        }
>      )
> 
> It possible in D ?
> How pass code block to template ?
> How to solve this problem ?

D does not have macros. Instead we have mixins. mixins allow you to 
write code as a string, and then interpret the code as if it were typed 
in the given location.

For example (and I'm not sure how you want to deal with M and D, this is 
one possibility):

string TPL(size_t M, SomeType D, string block) { // not sure what type 
of D should be

return "if((state & " ~ M.to!string ~ " && diraction == " ~ D.to!string 
~ ") " ~ block;
}

// usage:

mixin TPL(OPEN, OUT,
q{
     delete AppsWindow;
     state &= !OPEN;
});

-Steve